This invention relates generally to lawn mowing machines and more particularly concerns a rapid height-of-cut adjustment mechanism for lawn mowing machines. It is well known that the height-of-cut of mowing machines used, for example, to cut grass greens on golf courses, must be precisely controlled. In addition, it is customary to surround a golf course green with a collar or "froghair" cut at a slightly higher level as a transition portion, for the purpose of chipping and to vary the shots required of the golfer. To deal with this problem, a number of alternative mechanisms and methods have been used to cut the green and collar portions.
Often, separate mowers with separate height-of-cut settings will be used for the purpose of greens cutting and collar cutting applications. This results in substantial additional expense due to required duplication of machines and problems in transporting more than one machine to provide the greens cutting and trimming function.
Alternative rapid height-of-cut adjustment in the prior art is shown in U.S. Pat. No. 3,524,309 to Bartlett and U.S. Pat. No. 3,824,772 to Sorenson. In the Bartlett patent the height-of-cut adjustment is achieved by moving a ground engaging roller into contact with a two position stop. The switching is accomplished through a bell crank lever system. The Sorenson patent teaches use of alternative ground engaging rollers adjusted for the two positions. During operation of the lower roller setting the other roller is swung upward and out of ground contact.
Common drawbacks of prior art devices are that they are either difficult to actuate or do not provide precise adjustment with compensation for wear in the adjustment mechanism over the life of the cutting unit.
The present invention overcomes these difficulties by providing an easily actuated spring biased height-of-cut adjustment mechanism in which the spring biasing not only provides the triggering force to change from one setting to another but also takes up wear in the system and protects against wear caused by raising and lowering cutting units since the spring upwardly biases the pivot arms which carry the adjustable ground engaging roller.